Laminated glass plane with electrically controlled functional element

ABSTRACT

The invention concerns a laminated glass pane ( 1 ) with at least a rigid pane and a flat electrically controlled functional element ( 2 ) as well as at least a thin electrically conductive coat ( 5 ), wherein, in accordance with the invention, the coat ( 5 ) also constitutes a flat electrode of the functional element, the coat being capable of being heated by being powered with an electric voltage, independently of the power supply of the functional element ( 2 ). Thus, unwanted variations of the optical properties of the functional elements are reduced when such a laminated glass pane is used at highly fluctuating temperatures, in particular at low temperatures.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. counterpart of WO 03/056880, andclaims priority to German application number 01/10164063.3 filed on Dec.24, 2001, the entire contents of each of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a laminated panel assembly comprising at leastone rigid panel, an electrically controllable flat functional element,such as an electroluminescent lighting element, and at least oneelectrically conducting thin film.

2. Description of the Background Art

The term “laminated panel assembly” is understood here to mean a unitconsisting of a rigid panel and of the functional element, which isitself composed of several films and joined to the rigid panel, oralternatively applied thereto. The term “functional elements” isunderstood to mean, within the context of the present description, flatelements such as electroluminescent lighting elements or also panelelements with electrically controllable light transmission, for exampleelements of the liquid-crystal type. The respective functional elementtherefore has optical properties that can be electrically controlled.

It is not absolutely necessary to place the functional element betweentwo rigid panels of a laminated panel assembly, but this arrangementwill be preferred for safety reasons, given that there is possibly arather high supply voltage (for electroluminescent lighting elements).Placement in a laminated panel assembly furthermore protects thefunctional element from mechanical attack and from penetration bymoisture and dirt.

The material of the rigid panels may themselves in principle be chosenfreely; likewise, it is possible to use plastic panels or glass panels.It is also known that glass panel/plastic panel hybrid laminates can bemanufactured on an industrial scale.

Document EP-A1-0 267 331 teaches a laminated panel assembly for vehicleswith a sign placed in the adhesive layer of the laminate, which sign isrepresented or can be back-lit by an electroluminescent (EL) lightingelement. The necessary electrical conductors are rendered practicallyinvisible by using transparent conducting tracks or layers inside thelaminate. After the supply voltage has been applied, the luminous signalseems to float in the panel assembly without the conductors beingvisible. The aforementioned document presents two different types oflighting elements. In the first type two conducting electrodes areprovided on the same substrate, these being coated by the lightingelement, which in turn includes a junction electrode. From theelectrical standpoint, two capacitors connected in series are thusformed. In the second type, one of the two electrodes is respectivelydeposited in the form a thin transparent layer on the two internalsurfaces of the laminated panel assembly, and the lighting element isplaced between these surfaces. Also disclosed in that document, as anoption, is the fact that the output of light through one of the panelsmay be prevented by means of an opaque coating.

The prior German patent application 10126868.6 discloses a panel with aruled opaque coating, in which panel, at least in part of the opaquesurface portions, at least one flat EL lighting element consists ofseveral layers with a transparent electrode is provided, which lightingelement, after an electrical voltage is applied, emits light on the sidewith the transparent electrode of one of the flat faces of the panel. Alaminated panel assembly of this type can be used, for example, as aroof panel in a vehicle, which, when it is dark, illuminates thepassenger compartment by internal surface lighting.

For most fields of application of laminated panel assemblies, it isdesirable for the luminous tint from the EL lighting element to bepractically constant. When such EL lighting elements, made of a thickinorganic film of large area, operate, especially in motor vehicles, itturns out that differences in the color emitted may, however, resultwhen there are variations in temperature. Thus, an EL lighting elementat −20° C. will shine with a completely different color than at +80° C.,these temperature variations nevertheless being realistic during the useof a motor vehicle. A given luminous tint, whose color harmonizes, forexample, with its surroundings, can only be set for a certain limitedtemperature range.

The abovementioned literature does not tackle this problem. Admittedly,these lighting elements in operation gives off a certain amount of heatbecause of the power that they dissipate; however, in practice this isnegligible.

Trials carried out for the purpose of balancing the luminous tint byinjection of the frequency of the supply voltage result in a drasticreduction in the lifetime of the EL lighting element.

It is certainly possible, by using a temperature sensor, to completelyprevent the EL lighting element from lighting at low temperatures. Thus,negative effects of low-temperature operation on the lifetime of the ELlighting element are also avoided.

SUMMARY

The basic principles of electroluminescence have been known for a longtime. A detailed document and the luminous tints that can be achievedmay be obtained from the Internet address“http://dupont.com/mcm/luxprint/about.html” (situation: December 2001),so that it is necessary to go into details here only briefly.

A capacitor is produced from two conducting layers, one of which istransparent and lets light through. Deposited on the transparentelectrode, in the capacitor, is an opaque layer with light-emittingpigments and an insulating (dielectric) layer. If an AC voltage (usually100 V AC) is applied to the two electrodes of this element, this voltageinduces currents in the pigments, which in turn produce, by dispersionprocesses, light that leads through the transparent electrode.

The electrode layers, the electroluminescent layer itself and thedielectric layer may be deposited by thick film screen printing onsuitable substrates, such as glass or PET sheets. This known effectproduces surface lighting effects which can be used for many purposes(lighting, logos, luminous signs), if the relatively low light densityand the choice of colors, limited by the materials that can be used, areacceptable. Furthermore, the electroluminescent elements themselves(hereafter called lighting elements) are not transparent so that asurface provided with them cannot let light through (in daylight).

Electrically controllable panel elements are also known which work onthe basis of liquid crystals, the light transmission of which may bemodified by applying a voltage. These elements may also introduceundesirable variations in the instantaneous degree of transmission atextreme temperatures. Thus, such a panel element may, in the off state,in which it should in fact remain opaque, spontaneously becomestransparent at temperatures below −5° C.

It is known from many reports that thin transparent conducting films ofdoped oxides or of metals can be used as panel surface heating. For thispurpose, it is necessary to conduct, via suitable power supplies orelectrodes, a current over the area of the film, which because of itsohmic resistance heats up. As a general rule, such films constitute onepart of a multilayer system composed of several thin films, this beingmost of the time transparent to visible light, which may also havethermal insulation or reflection properties. The thin films are filmsdeposited by a process other than screen printing. It is also known touse controls that act automatically with sensors, whereby a panel (of avehicle) is automatically heated, for example in order to remove foggingon the inside of this panel.

The object of the invention is to reduce the temperature-inducedvariations in the properties of an electrically controllable functionalelement placed on or in a laminated panel assembly.

In accordance with the invention, this objective is achieved by the factthat the film forms at the same time a flat electrode of the functionalelement, this film being able to be supplied with an electrical voltageand heated independently of the power supply for the functional element.

The features of the secondary claims represent advantageous improvementsof this subject matter. A method for using a functional element combinedwith a laminated panel assembly is also disclosed.

Thus, the functional element is coupled to a surplus heating film whichmakes it possible, in all cases at low ambient temperatures, to increasethe temperature of the functional element up to the range in which itsoptical properties, for example the tint of the light emitted, weredesigned.

In a preferred variant, the power, or current, supplied to the heatingfilm is automatically controlled by means of a temperature sensor. For atemperature value measured by the temperature sensor below apredetermined threshold, the functional element is heated until themeasured temperature lies within the desired or defined range.

The system can work with a measurement of the ambient or externaltemperature, or else the temperature inside the passenger compartment ofa vehicle as the measurement quantity. However, it will be preferable toplace the temperature sensor as close as possible to the functionalelement, for example by integrating it into the laminated panelassembly, so as to obtain as sensitive as possible a response of thetemperature control to the actual temperature of the functional element.

In principle, the laminated panel assembly may be provided with aseparate transparent heating film, which is not functionally coupled tothe functional element. However, it is particularly advantageous to alsouse, for the possible heating, one of the electrode films that it is inany case necessary to provide for the functional element. The electricalsupply for the heating function may be provided using a DC voltage,which is applied to two electrodes on each side of the functionalelement. For uniform coupling of the voltage potential within thetransparent electrode (ITO film), a broad conducting track is in anycase required. Consequently, only one further electrode is required, theposition of which must be chosen in accordance with the heating voltagechosen. To obtain sufficient heating power for low supply voltages (forexample a DC voltage of 12 V, the busbar distance must be short, in anycase less than the width.

The current flowing between the two electrodes heats the film and thefunctional element attached to the surface of said film; however, itdoes not affect the power supply (AC voltage) for the functionalelement.

In principle, it matters little in this case whether the functionalelement is placed or printed directly on one face of a rigid panel or ismanufactured on a particular support such as, for example, a sheet ofPET, which will subsequently be suitably joined to the rigid panel orlaminated into a composite. In both configurations, the heating film mayeither be placed between the rigid panel, or the supporting sheet, andthe functional element or be placed on the opposite side of thefunctional element from the panel or the supporting sheet.

In addition to the positive effect on the properties of the functionalelement, in particular the better color constancy of an EL lightingelement, this heating film furthermore allows the thermal comfort in avehicle to be improved, specifically when the laminated panel assemblyis placed in the roof region.

The ratio of the area of the functional element to the total area of thepanel can also be chosen freely. If required, several functional orlighting elements with possibly different colors and shapes may beplaced together side by side.

Finally, it may also be beneficial, for particular applications, to emitlight from one or more electroluminescent lighting elements on bothplane faces of the panel assembly. In this case, a separate opaquecoating is unnecessary because the electroluminescent layers themselvesdo not let visible light through. In principle, it is also possible to“stack” several electroluminescent lighting elements of this kind, oneon top of another, possibly with orientations differing from oneanother, for which a common intermediate electrode may optionally beemployed. This intermediate electrode may again also serve as heatingfilm in accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front view of a panel assembly with an EL lightingelement and electrical heating coating.

FIG. 2 shows a sectional view of the device shown in FIG. 1.

FIG. 3 shows the device of FIG. 2 with two rigid panels joined by aninterlayer, in which assembly a functional element and thin film arehoused within the interlayer.

FIG. 4 shows a device with multiple functional elements provided side byside.

FIG. 5 shows a device with multiple electro luminescent lightingelements provided one on top of another.

DETAILED DESCRIPTION

Further details and advantages of the subject matter of the inventionwill become apparent from the drawings of illustrative examples and fromthe detailed description which follows. The description is given withreference to an EL lighting element, without however wishing to thusexclude other functional elements for this application.

FIG. 1 shows, in a simplified representation and as an example, a viewof a panel assembly with an EL lighting element and an electricalheating coating.

A rigid panel 1 supports an EL lighting element 2, which extends overpractically the entire area of the surface of the panel 1, but whichleaves a peripheral edge region 3 of the panel free. A dotted line 4denotes the boundary of an external edge strip on the face of the panel,which may be covered by an opaque colored film which serves as visualprotection. Of course, this boundary may also lie within that area ofthe surface of the panel 1 which is covered by the EL lighting element2; said boundary has been shown here outside this surface region onlyfor the sake of clarity.

Placed under the EL lighting element 2 is an electrically conducting,preferably transparent, film 5 which extends over the entire area of thepanel 1 and also covers the edge strip rendered opaque. A distance of afew millimeters between this film 5 and the edge of the panel will alsobe maintained—in a manner known per se—so as to prevent corrosion. As ageneral rule, the film 5 forms part of a multilayer system, the colorand reflection properties of which can be adjusted over a wide rangeaccording to the requirements by a targeted definition of thethicknesses and materials of the individual layers. However, for thefunction described here, it is essentially only the electricalconductivity and the heating capability of at least one of theindividual layers that are important. The film 5 may, for example, becomposed of indium tin oxide (ITO), but also of a metal, for examplesilver.

This film 5 forms one of the flat electrodes of the EL lighting element2 constructed overall as a capacitor, preferably the ground electrode.If light from the lighting element has to be emitted through thiselectrode, it must of course be transparent to visible light. Theelectrical supply (AC voltage) for the other side of the EL lightingelement 2 is indicated by a lead 6, which is insulated from the film 5and is connected, in a manner not shown in detail, to the second flatelectrode of the EL lighting element 2. The lead 6 is connected, in amanner not shown, to another flat electrode on one side of the ELlighting element 2, in this case at the top.

Two other leads 7 and 8 serve to supply the film 5 with a supply voltage(DC voltage). All the leads are placed in a corner region of the panel1. The leads 7 and 8 are connected electrically to conducting tracks 7′and 8′. The conducting track 7′ extends from the corner of the panelalong the long lateral upper side of the panel (as in the drawing) asfar as a point close to the following corner of the panel. Theconducting track 8′ firstly runs along a short side of the panel 1,describes a tight arc around a corner of the panel and then extendsalong the lower lateral side of the panel as far as a point close to thefollowing corner.

The conducting tracks 7′ and 8′ (in conventional panel heating systems,the tracks are also called collector rails) may be produced in the formof thin bands which are suitably fixed to the panel. However, they mayalso be applied to a rigid panel by screen printing a conductiveprinting paste and then baked, for example when bending and/ortoughening a glass panel. In all cases, they are electrically connectedover a large area to the electrically conducting film 5 and may lieeither above or below the film 5. If necessary, the film could even becontained between two conducting tracks deposited one after the other(one before the film is applied and the other afterwards). Furthermore,the conducting tracks 7′ and 8′ are placed in such a way that theycontain, between them, the surface of the film 5 covered with the ELlighting element 2. Likewise, they are placed in a manner concealed fromsight in that edge region of the panel 1 rendered opaque. Of course,another visual mask may also be provided on the other side of the panelthat can be seen here.

By means of a separating line 9 made in the film 5 parallel to the shortside, the conducting track 8′ is separated from the rest of the field ofthe film with a high ohmic resistance. This measure is necessarybecause, or when, the two leads 7 and 8 are relatively close to oneanother. Admittedly it is thus simpler for electrically contacting themwith the outside (for example it is possible to use an assembly commonto several pins or by cross connection), however, without the separatingline 9 the heating current would flow along the shortest path, andtherefore in practice directly between the leads 7 and 8 through thefilm 5.

If necessary, such separating lines may also provided for electricallyinsulating the lead 6 from the film 5, in the region where it covers thefilm 5. One possible embodiment with two separating lines, on each sideof the lead, is indicated by the dot-dash lines in the figure.

The configuration illustrated here, of conducting tracks and leads,ensures that, by applying a DC voltage to the leads 7 and 8 and to thosetwo portions of the conducting tracks 7′ and 8′ running horizontally (inthe drawing), a current flows which is uniformly distributed over thearea of the conducting film 5. The film 5 serves in this case as theground electrode for the EL lighting element 2. One of the conductingtracks, 7′ or 8′, forms the common point for collecting the outgoingcurrent, both for the EL lighting element 2 and for heating the film.

The electrical resistance of the film (typical surface resistances ofsuch films lie between 2 and 4 Ω/square) results in heating when acurrent flows. The heating power produced is used for the targetedadjustment of the temperature of the EL lighting element 2. For thispurpose, a temperature control 10 is provided, which determines theactual temperature of the EL lighting element 2 with (at least) atemperature sensor 11 (for example a PTC element to be laid flat)directly in or on the laminated panel assembly 1. It forms part of acentralized control 12, shown only schematically, which is in turnconnected to a power supply for the power and measurement/controlcurrents and which manages all the electrical functions of the panel 1,in particular also the electrical supply for the EL lighting element 2.If the panel is an electrically operated moving panel (roof panel) in avehicle, the centralized control may then also include the control forits position. The temperature control 10 comprises in any case thestructural and switching elements that are needed to adjust a setpointtemperature in the region of the temperature sensor 11. In particular,it will automatically apply the supply voltage needed for the leads 7and 8 when the temperature sensor indicates that the actual temperatureis below a predetermined value, and it will cut off the supply voltagewhen a predetermined setpoint temperature is again reached.

Where appropriate, this may also occur when the vehicle is at rest, whenany undesirable transparency of a panel element with electricallycontrollable light transmission must be prevented.

Of course, any thermal damage to the EL lighting element 2 due to theheating is excluded by limiting the heating power, or alternatively themaximum temperature that can be achieved. Even if the heating of thepanel 1 by means of the film 5 has to be able to be triggered in anotherway, in particular manually, any additional heating must then beprevented by means of the temperature sensor 11 when further heating, inan already hot environment, would run the risk of thermally damaging theEL lighting element 2.

Finally, the temperature control, or alternatively the centralizedcontrol, may be configured in such a way that the EL lighting element 2can be switched on only when the temperature lies within a range thatdoes not prejudice its operation. This means that its operation couldalso be prevented, for example, even in the case of extreme ambienttemperatures.

FIG. 2 shows a cross-sectional view of the rigid panel 1 connected tothe thin film 5 which is in turn connected to the functional layer (ELlighting element) 2. The electrode 6 is positioned in contact with thefunctional layer 2. The leads 7 and 8 also are shown contacting the thinfilm 5.

FIG. 3 shows two rigid panels 1 joined by an interlayer F1, in whichassembly a functional element 2 and thin film 5 are housed within theinterlayer.

FIG. 4 shows plural functional elements provided, side by side, to beoperated independently of one another, which include a common electrode(shown here as thin film 5). A network of wires 13 or equivalentdispatch power to each functional element from the electrode 6. Theleads 7 and 8 are shown connected to the thin film 5.

FIG. 5 shows a laminated panel assembly with two electroluminescentlighting elements 2 and 2′ provided, one on top of another, to beoperated independently of one another, but including a common centralelectrode 5. The electroluminescent lighting elements 2 and 2′ areconnected to the electrodes 6 and 6′, respectively.

1. A laminated panel assembly comprising: at least one rigid panel; anelectrically controllable flat functional element; and at least oneelectrically conducting thin film that forms a flat electrode of thefunctional element, the thin film being connected to receive anelectrical voltage that heats the thin film independently of a powersupply for the functional element.
 2. The laminated panel assembly asclaimed in claim 1, wherein the thin film is configured to be suppliedautomatically with the electrical voltage according to a temperaturesignal sent to a temperature control from a temperature sensor.
 3. Thelaminated panel assembly as claimed in claim 2, wherein the temperaturesensor is combined in a space with the functional element and determinesan actual temperature of the functional element.
 4. The laminated panelassembly as claimed in claim 1, wherein the functional element covers atleast part of a surface of the thin film.
 5. The laminated panelassembly as claimed in claim 1, wherein the thin film is in electricallyconducting contact with at least two conducting tracks configured todeliver a supply voltage for heating of the functional element, whichtracks are placed on either side of the functional element covering thethin film.
 6. The laminated panel assembly as claimed in claim 1,wherein the functional element is mounted directly on the rigid panel.7. The laminated panel assembly as claimed in claim 1, wherein thefunctional element is mounted on a specific supporting substrate.
 8. Thelaminated panel assembly as claimed in claim 1, comprising at least tworigid panels and an interlayer joining the at least two rigid panelstogether, in which assembly the functional element and the thin film arehoused within the interlayer or are placed on an internal face of one ofthe at least two rigid panels.
 9. The laminated panel assembly asclaimed in claim 1, wherein plural functional elements are provided,side by side, to be operated independently of one another, which includea common electrode.
 10. The laminated panel assembly as claimed in claim1, wherein at least two electroluminescent lighting elements areprovided, one on top of another, to be operated independently of oneanother, which include a common central electrode.
 11. The laminatedglazing panel as claimed in claim 10, wherein the common centralelectrode is configured to be used as heating film.
 12. A method forusing a functional element having electrically controllable properties,combined with a laminated panel assembly, in which the laminated panelassembly comprises at least one rigid panel and at least oneelectrically conducting film, wherein the electrically conducting filmis connected to receive an electrical voltage that heats the thin filmindependently of a power supply for the functional element, when anactual temperature of the functional element, determined by atemperature sensor, is below a predetermined setpoint temperature. 13.The method as claimed in claim 12, wherein the power supply for thefunctional element is configured to be operated only if the setpointtemperature of the functional element is set.
 14. The method as claimedin claim 12, wherein a flat electrode of the functional element issupplied with the electrical voltage and heated.